Collation is the process of sorting pages of multiple copies of a document so that the pages of each copy are contiguous and ordered (i.e. all the pages of copy one are contiguous, all the pages of copy two are contiguous, and so on). Traditionally, collation has been performed mechanically using output bins or original re-feeding. In the former case, as each page of the original is copied, each copy is placed in a different bin. When the required number of copies of a page has been made or the number of available bins has been exhausted, the next page is copied in a similar fashion. This process is continued until all pages have been copied. Mechanical output bin collation suffers from a number of limitations. First, the number of collated copies that can be printed cannot exceed the number of bins available. Second, the number of pages in a single copy cannot exceed the capacity of an output bin.
The mechanical limitations associated with the use of sorting bins can be overcome by re-feeding the original pages once for each copy. Using this technique, collated copies are stacked upon each other in a single output bin. Although this technique avoids the problems associated with the use of multiple output bins, it introduces another serious shortcoming: performance. Each page of the original must be fed into the hardcopy device multiple times. This process requires extra time and introduces additional potential for mechanical failure. In contrast, when using output bins to collate, it is only necessary to feed each page of the original once, thus reducing the potential for mechanical failure and avoiding the time required to repeatedly feed the original pages.
In digital hardcopy devices, the mechanical and performance problems associated with re-feeding original pages have been largely eliminated. Rather than physically re-feeding original pages, each original page is digitized—a process by which the page information is converted into a digital form suitable for use in a digital computing system—and recorded into storage (e.g., RAM (random access memory) or disk) for subsequent use. As each copy is produced, the pages of the original are “digitally re-fed” by retrieving them from storage; the digital version of original page is used to produce a copy of that original page. Because the original pages are not physically re-fed, the risk of mechanical failure is drastically reduced. Furthermore, performance is dramatically improved because the digital version of the original page can typically be retrieved much faster than the original page can be mechanically re-fed. This process is henceforth referred to as “electronic collation” or “digital collation.”
Printers, being digital hardcopy devices, can also take advantage of digital collation. Unlike copiers, printers receive the original already in digital form. Typically, this digital form is translated within the printer into another digital form referred to as “print ready.” When in print ready form, original pages can be retrieved and printed at a speed that at least matches that of the print engine. In order to produce collated copies, printers will record the print ready form of the original into storage for subsequent use. Similar to copiers, as each copy is produced, the print ready form of the pages of the original are digitally re-fed by retrieving them from storage; the print ready digital form of each original page is used to produce a printout of that original page.
Digital collation works well, provided the digital hardcopy device has adequate digital storage. If the amount of storage is not adequate to store all of the original pages inprint ready form, digital collation fails. Rather than faithfully printing the number of collated copies requested, only a single copy is typically printed; it is not possible to print additional copies because it is not possible to store the original in its entirety.
With hardcopy devices that utilize disk drives to store the original pages in digital form, exhausting the amount of available storage is rare. However, very few hardcopy devices (less than 10%) have a hard disk installed. For the majority of printers (e.g., the HEWLETT-PACKARD (TM) LASERJET (TM) model 4050 printer), digital collation is performed using RAM storage. Because of the relatively high cost of RAM per megabyte in comparison to hard disk storage, the amount of storage that is provided through RAM is severely limited. This drastically increases the chances that available storage will be exhausted when using digital collation to print.
When available storage is exhausted during a digital collation operation, there is currently no reliable way to recover or to even notify the end-user who originated the print job. This means, for example, that if a reasonably large document is printed using digital collation, only a single copy of the document will print—without warning or explanation that the additional copies did not print.
SUMMARY OF THE INVENTION
In one respect, the invention is a method for printing N collated copies of a document on a printer, where N is an integer greater than one. The method determines whether the printer has sufficient capacity to print N collated copies of the document. If the printer has insufficient capacity to store one copy of the document, then the method performs the following step N times: sending a single copy of the document to the printer. The capacity may be memory to store one copy of the document in print ready form.
In another respect, the invention is a computer readable medium on which is embedded a program that performs the method described above.
In yet another respect, the invention is an apparatus for processing an incoming print job requesting N collated copies of a document on a printer, where N is an integer greater than one. The apparatus comprises a memory, a spooler connected to the memory, a status agent and a control logic connected to the spooler and the status agent. The memory is configured to store the document. The spooler is configured to send an outgoing print job to the printer. The status agent is configured to receive from the printer information regarding whether the printer has sufficient capacity to collate the document. The control logic controls the spooler on the basis of this information.
In comparison to known prior art, certain embodiments of the invention are capable of achieving certain advantages, including some or all of the following: (1) printing of the correct number of copies in almost all cases transparently to the user; (2) automatic detection of and compensation for limitations due to inadequate storage capacity; and (3) relaxation of device memory requirements, allowing, for example, production of printers with less expensive RAM memory without sacrificing digital collation performance. Those skilled in the art will appreciate these and other advantages and benefits of various embodiments of the invention upon reading the following detailed description of a preferred embodiment with reference to the below-listed drawings.